1. Field of the Invention
The present invention relates, in general, to linear actuators and, more specifically, for linear actuators for positioning vehicle seat components.
2. Description of the Art
Vehicle seat assemblies are usually provided with a seat adjuster for adjusting the horizontal fore and aft position of an upper track movably mounted in a lower track fixed to the vehicle, and with a seat recliner for adjusting the angular position of a pivotable seat back with respect to a seat cushion. One type of seat adjuster includes a plurality of discrete, spaced positions or detents for releasibly locking the upper track to the lower track.
Another type of seat adjuster which is also usable as a seat recliner utilizes a linear actuator formed of a threadingly engaged lead screw and nut to provide an infinite number of user selectible seat adjustment positions. Various means are utilized to releasibly lock the nut in a fixed position to prevent rotation of the nut and the lead screw so as to fix one of the movable components of the seat in a user selected, adjusted position with respect to other components of the vehicle seat. While the latter described type of linear actuator is capable of providing infinite seat adjustment positions, such a linear actuator still lacks a reliable, smooth release operation, particularly when seat adjustment is made under load, i.e. the user's weight on the seat.
Further, vehicle seat assemblies are either a power driven or a manually operated type. Due to the different functional requirements of a power driven and a manually operated seat adjuster and/or seat recliner, particularly with respect to the common use of spaced detents engaged by a manually operated locking bar in a manually operated seat adjuster, different track assemblies are necessary for each power driven or manually operated seat adjuster and/or seat recliner. This has resulted in a proliferation of different types of seat assemblies which detracts from the advantages attainable by commonality of components for all power driven or manually operated vehicle seat assemblies.
Thus, it would be desirable to provide a linear actuator for a vehicle seat which provides a smooth, reliable lock and lock release. It would also be desirable to provide such a linear actuator for a vehicle seat which provides an infinite number of seat adjustment positions. It would also be desirable to provide a linear actuator for a vehicle seat which enables a common seat assembly design, including the seat tracks and a major portion of the drive mechanism, regardless of whether the seat assembly is power driven or manually operated. Finally, it would be desirable to provide a linear actuator for a vehicle seat which has a simplified construction, reliable operation, a small overall size, low weight and low cost.